Vacuum pump



INVENTOR. MARVIN SKOLNIK NUM, M, 1956 M. sKoLNlK VACUUM PUMP Filed Dec. 4, 1952 2,770,414 VACUUM PUMP Marvin Skolnik, Cleveland Heights, Ohio, assignor to The Weldon Tool Company Application December 4, 1952, Serial No. 324,005 8 Claims. (Cl. 230-149) The invention relates in general to fluid devices such as pumps or motors and more particularly to method and means of sealing the moving parts in a fluid device to achieve greater fluid differential pressures between the fluid inlet and outlet.

in prior art fluid devices using a moving blade and rotor type of vacuum pump, at least two variable volume chambers are created between the rotor and housing by the blades. All of such chambersV sucked air or gas from the chamber to be evacuated. Oil was provided in some manner to provide lubrication and to help seal the working clearance apertures between the blades, rotor, and housing. Only a line contact can effectively be maintained between the blades and the rotor and the oil lm therebetween would be ruptured at high differential air pressures, thus limiting the pressure or vacuum capacity of the pump and also destroying the vacuum previously created.

The present invention relates to a method and means for maintaining one of the chambers full of oil to act as a reservoir, and using another chamber as the vacuum pump portion of the structure. ,The reservoir assures a continuous supply of oil to provide the oil iilm for lubrication and sealing, and if thehigh diilerential air pressure tends to rupture any sealing oil film, no harm is done. No air can be sucked in to destroy the vacuum, since the reservoir of oil will immediately replace the oil in the lm which is being sucked into the vacuum chamber through the working clearance apertures.

An object of the invention is to create a better vacuum in a vacuum pump.

Another object of the invention is to obtain a better differential gas pressure between the inlet and outlet of a fluid device whether pump or motor.

Still another object of the invention is to provide an oil film to seal moving parts of a pump.

Still another object of the invention is to utilize an oil or liquid reservoir to seal the moving parts of a pump or motor.

Still another object of the invention is to continuously maintain an oil iilm between two relatively movable parts in a variable volume chamber of a fluid pump or motor.

Still another object of the invention is to continuously maintain an oil film between a movable part and a housing wherein the movable part creates two variable volume chambers and is common to both.

Still another object of the invention is to provide a method for obtaining a large differential fluid pressure in a pump or motor.

Still another object of the invention is to provide for passing a first fluid through a fluid device and using a second lluid for sealing the cracks or apertures in the fluid device wherein the first iluid has a greater ability than the second fluid to penetrate the aperture.

Other objects and a fuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

Figure l is a longitudinal sectional view through a vacuum pump embodying the invention;

Figure 2 is an enlarged sectional View taken on line 2--2 of Figure l;

Figure 3 is a view of the cover taken on line 3-3 of Figure 1;

nited States Patent O 2,770,414 Patented Nov. 13, 1956 ICC Figure 4 is a sectional view of the cover taken on the line 4-4 of Figure 3; and

Figure 5 is a sectional view taken on the line 5-5 of Figure 2.

The gures of the drawing show a specific embodiment of the invention wherein the reference number 11 indicates a complete pump. This pump is generally similar to that shown in the J. P. Johnson Patent No. 2,452,468. The pump 11 has a housing 12 and a cover 13 fastened together with screws 14. The housing 12 has a flange 15 which may be fastened to a motor, not shown, and a pump may be driven by a motor shaft 16.

The housing 12 has a wall 17 defining a cylindrical bore. A housing insert 18 is pressed into the cylindrical bore 17. The housing insert 18 has a wall 19 defining another cylindrical bore. The housing insert 18 has first and second radially disposed slots 20 and 21. Blades 22 and 23 fit closely within these slots and are adapted to move radially. An eccentric rotorl 24 having three lobes is journalled for rotation within the cylindrical bore 19. The rotor 24 is integral with a pump shaft 25, which is adapted to be driven by the motor shaftL 16. The pump shaft 25 is journalled in the insert 18. A spring 29 made of wire engages the outer portions of each of the blades 22 and 23 to urge them inwardly into engagement with the rotor 24. Stop pins 32 keep the spring 29 in place. Since the bore 19 is cylindrical and the rotor 24 has three lobes, the rotor 24 will have an area contact with the bore 19 at three diierent places. Since the rotor rotates and co-operates with the blades 22 and 23 and the housing insert 18, at least two variable volume chambers are established. Reference characters 30 and 31 indicate first and second variable volume chambers.

The cover 13 has three openings including an air inlet 34, an oil inlet 35, and a combined outlet 36. A shallow groove 33 in the cover 13 communicates with the outlet 36 to collect any oil leaking between the cover 13 and the housing 12 and direct it to the outlet 36. The air inlet 34 is shown diagrammatically in Figure 3 as being connected to a chamber 37 which is to be evacuated of air or gas. A gauge 38 is shown connected to this chamber 37. The oil inlet 35 is shown connected to an oil tank 39, and the combined outlet 36 is shown connected to dis charge oil and air to the tank 39. A valve 40 is connected on the air vent from the tank 39. The housing insert 18 has four axially parallel bores 41, 42, 43, and 44. The bores 41 and 42 are diametrically opposite with the bore 41 leading to a passageway 45 and the bore 42 leading to a passageway 46. The cover 13 has a plug 47 in a recess 48. The plug 47 is cut away at 49 and 50 to form chambers 51 and 52. The passageway 45 communicates with the chamber 51, and the passageway 46 communicates with the chamber 52. Axially parallel holes 53 and 54 are bored in the plug 47 and communicate with the chambers 51 and 52. The holes 53 and 54 are aligned with the bores 41 and 42 to thus become inlet ports for the pump housing. The oil inlet is thus from the tank 39 through the inlet 35, the passageway 45, the chamber 51, and the bore 53 to the bore 41. The air intake is thus from the chamber 37 through the air inlet 34, the passageway 46, the chamber 52, and the bore 54 to the bore 42.

The housing insert 18 cti-operates with the housing 12 to form an annular manifold 57. The combined outlet 36 is connected to the manifold 57 by a bore 58. Figure 5 best shows that the manifold 57 is connected by a passageway 59 to the bore 43 which is the oil outlet. A similar passageway connects the manifold 57 to the bore 44 which is the air outlet.

A seal cage 63 surrounds the shaft 25 and contains an 0-ring 64. The planar surface of the seal cage 63 that abuts the insert 1S is lapped therewith for an oil-tight seal. A -spring 65 urges the seal cage 63 against the insert 18. Oil that may escape between the shaft 25 and the insert 26 is collected in a collector groove 66 and returned by a passageway 67 to one of the inlet bores 41 and 42.

Operation When the structure is being used as a vacuum pump, the valve 4t) will be opened to vent the tank 39 to atmosphere. The Figure 2 shows that the direction of rotation is counterclockwise; hence, the first variable volume chamber 30 becomes smaller as the second variable volume chamber 31 becomes larger. Since bore 41 is an oil inlet, the first chamber 30 will be full of oil which is being exhausted to the oil outlet 43 and the second chamber 31 will be sucking air through the air inlet 42 from the chamber 37. ln the prior art usages of similar devices, both inlets of the pump would be connected to the chamber 37 to evacuate same. in this invention only one inlet of the pump is connected to the chamber 37 whereas the other inlet of the pump is connected to the oil tank 39. This means that oil is circulated through the upper half of the pump, as seen in Figure 2, from the inlet bore 41 to the outlet bore 43. Thus, the space between the rotor 24 and the housing insert 13 in the upper half of the pump is continually full of oil. This creates a reservior of toil in the first variable volume chamber 30. The spring 29 urges the blade 23 against the rotor 24. There are bound to be imperfections in the surfaces of these elements to thus form a crack or small aperture there between. Since the bore 42 is an air inlet, there will be a large differential fluid pressure between the bore 42 and the bore 43 which is at atmospheric pressure. If the high vacuum at the inlet bore 42 tends to pull the film of oil out from between the blade 23 and the roto-r 24, the vacuum is not destroyed because the reservoir of oil in the variable volume chamber 30 will continually maintain this oil film and prevent gas communication between the bores 42 and 43.

In the prior art form wherein both sides of the pump were used as a vacuum pump, there was a large differential air pressure between the bores 4.2 and 43 just as in the present case. Such prior art pumps were, of course, lubricated and lan attempt was made to establish an oil film which would seal the blade to the rotor. Such prior art pumps of this description could draw about twentyseven inches of mercury in differential vacuum pressure, with 29.92 inches of mercury being standard atmospheric pressure. In such prior art structures, it was relatively easy for the yoil film between the blade and the rotor to be destroyed by this large differential gas pressure since only a line contact between the blade and the rotor can be provided. In such prior art devices, it was frequently found that the vacuum pressure built up by the pump would periodically be broken down and the pump would again have to build up to this maximum differential pressure of about twenty-seven inches. in the present invention, even though only onehalf of the volumetric capacity of the pump is used for evacuation of gas, the pump is capable of drawing a differential pressure of about twentyanine and one-half inches of mercury which is approximately six times as good a vacuum as the prior art structure using twice the volumetric capacity.

The reservoir of oil in the upper half of the pump also provides a continuous oil film between the 4rotor lobes and the housing insert 18 and also between the planar faces of the rotor 24 relative to the insert 18 and the plug 47. A small working olea-rance must7 of course, be maintained at these planar faces so that the rotor 24 may rotate. Such continuously maintained reservoir of oil effectively seals this small working clearance to prevent leakage of air at any of these locations.

y The oil being circulated through one-half of the fluid device creates a better seal and thus establishes a much higher vacuum from the pump because the air has a greater ability than the oil to penetrate a crack or aperture. The oil may be considered a second fiuid which seals the pump so that it may maintain a better differential pressure of a first uid. When the second fiuid is a liquid, the desirable properties of such a liquid are that it shall have adequate Viscosity, a goed film strength, and preferably a low vapor pressure. Oil fullfills these irequirements when used with air or most gases as the first iiuid. Also, oil can provide the necessary lubrication. A differential gas pressure of approximately sixty to one, instead of ten to one, is thus obtained between the air inlet and the air outlet, and this with the same working clearances between moving parts.

If the valve 40 is closed, the pump may be used to build up an air pressure within the tank 39 so that the pump may operate as a pressure pump rather than a vacuum pump. It is to be noted that the rotor is a common part which moves between the first and second variable volume chambers; and since it moves from the first chamber containing oil to the second chamber containing air7 it will carry with it oil toy continuously maintain the oil film` throughout the lower half of the pump as seen in Figure 2. This will maintain the oil film between the motor lobe and the housing insert 18 as that particular lrotor lobe passes through the lower half of the pump.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure :of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

Y 1. A fiuid motor or pump, comprising, a housing, a wall in said housing deiining a bore, a rotor -rotatable in said bore, one of said rotor and housing having a cam surface, the other of said rotor and housing having slots and blades slidable in said slots, spring means engaging said blades to urge same into engagement with said cam surfaces, said blades in co-operation with said cam surface dividing said bore into first and second variable volume chambers, engagement of said blades with said yearn surface forming first and second interfaces, an inlet port adjacent one blade and an outlet port adjacent the other blade in each chamber, means connecting said outlet ports together and to a liquid storage tank, means introducing into said first chamber a first fluid exclusively and means introducing into said second chamber passing a second different uid exclusively, seal means including `said exclusive circulation of said second fluid through said second chamber sealing ysaid first and second interfaces thereby maintaining a high pressure differential between said first and second variable volume chambers.

2. A pump, comprising, a housing, a cylindrical wall in said housing defining a bore, walls in said housing defining slots, blades slidable in said slots, a lobed rotor having an .axis of rotation concentric with said bore, a spring engaging said blades to urge same into engagement with said rotor, said blades in co-operation with said rotor dividing said bore into first and second variable volume chambers, engagement of the inner surfaces of said blades with said rotor forming first and second interfaces, an inlet port adjacent one blade and an outlet port adjacent the other blade in eac-h chamber, means connecting said outlet ports together and to a liquid storage tank, means introducing only a gas into said first chamber and means introducing only a liquid into said second chamber from said liquid storage tank to continuously coat said rotor 'as it passes through said second chamber to seal the same with respect to said housing to increase the liuid pressure differential between the inlet and outlet ports of said first chamber, seal means including said exclusive introduction of liquid into said second variable Volume chamber sealing said first and second interfaces thereby maintaining a high pressure differential between said first and second variable volume chambers.

3. A vacuum pump, comprising, a housing, a cylindrical wall in said housing defining a bore, walls in said housing defining generally radially disposed slots, blades slidable in said slots, a spring engaging the outer surfaces of said blades to urge same inwardly into said bore, a lobed rotor having an axis of rotation concentric with said bore, said blades in co-operation with said rotor dividing said bore into two variable volume chambers, engagement of the inner surfaces of said blades with said rotor forming first and second interfaces, an inlet port adjacent one blade and an outlet port adjacent the other blade in each chamber, means connecting one of said outlet ports to a liquid storage tank, means connecting one of said inlet ports to `a gas line for gas evacuation thereof and the other of said inlet ports to said liquid storage tank to exclusively circulate liquid through only one of said variable volume chambers of said pump to continuously coat said rotor, as it passes through said one of said variable volume chambers, with :a liquid film to seal the same witlh respect to said housing, seal means including said exclusive circulation of liquid through said one of said variable volume chambers sealing said first and second interfaces thereby maintaining a high pressure differential between said two variable volume chambers. C u

4. A vacuum pump, comprising, a housing, a cylindrical wall in said housing defining a bore, walls in said housing defining generally two radially disposed slots, blades slidable in said slots, a spring engaging the outer surfaces of said blades to urge ysame inwardly into said bore, engagement of the inner surfaces of said blades with sai-d rotor forming first and second interfaces, a rotor having an axis of rotation concentric with said bore, said rotor being triangular and making an area contact with said bore at three substantially equally disposed locations on the periphery of said rotor, said blades in co-operation with said rotor dividing said bore into two variable volume chambers, an inlet port adjacent one blade and an outlet port :adjacent the other blade in each chamber, said outlet ports being connected together and connected to a liquid storage tank, means connecting one of said inlet ports to a gas line for gas evacuation thereof .and mean-s connecting the other of said inlet ports to said liquid storage tank to circulate liquid exclusively through one of said variable volume chambers, seal means including said exclusive .circulation of liquid through said one of said variable volume chambers sealing said first and second interfaces thereby maintaining a high pressure differential between said two variable volume chambers. v

5. In a vacuum pump having a lobed rotor within a housing and two radially sliding blades in the housing and co-operating with the movable rotor to establish first and second variable volume chambers, said housing having an outlet and an inlet port adjacent opposite sides of each blade, the method of sealing the blades to the rotor to prevent gas passage therethrough from said first to said second variable volume chamber, comprising, establishing one of said inlet ports as ra gas inlet from a chamber to be evacuated, establishing another of said inlet ports as a liquid inlet from a liquid tank at substantially atmospheric pressure, introducing only gas'into said gas inlet, introducing only liquid into said liquid inlet, rotating said rotor whereby liquid is circulated through one half of said pump to continuously fill only saidsecond variable volume chamber with liquid acting against the second chamber side of each of said blades to seal lche blades against the rotor so that the first variable volume chamber will evacuate gas from said chamber without gas leakage from said liquid outlet port past one of said blades to said gas inlet port. l

6. In a vacuum pump having a lobed rotor within a housing and two radially sliding blades in the housing and co-operating with the movable rotor to establish first and second variable volume chambers, said housing having an outlet and an inlet port adjacent opposite sides of each blade, the method of scaling the blades to the rotor to prevent gas passage therethrough from an outlet port to an inlet port, comprising, establishing one of said inlet ports as a gas inlet from a chamber to be evacuated, establishing another of said inlet ports as an oil inlet from an oil tank vented to be at substantially atmospheric pressure, combining said two outlet ports and directing same to said oil tank, introducing only gas into said gas inlet, introducing only oil into said oil inlet, rotating said rotor whereby oil is circulated through one half of said pump to continuously fill only said second variable volume chamber with oil acting against the second chamber side of eaoh of said blades to seal the blades against the rotor so that the first variable volume chamber will evacuate gas from said 4chamber without gas leakage from said oil outlet port past one of said blades to said gas inlet port.

7. A vacuum pump comprising a housing having a three lobed rotor rotatably mounted therein, said lobes engaging said housing at arcuately spaced positions and making area contacts therewith, walls within said housing defining first :and second radially extending slots, first and second vaiies movable within said first and second slots respectively and engageable at their inner extremities with said rotor to form first and second variable volume chambers on opposite sides of each vane, spring rrieans urging said first and second vanes into engagement with said rotor thereby forming first and second interfaces therebetween, a gas intake conduit communicating with said first variable volume chamber adjacent said first vane, a gas exhaust conduit communicating with said first variable volume chamber adjacent said second vane, a liquid intake conduit communicating with said second variable volume chamber adjacent said second vane, a liquid exhaust conduit :communicating with said second variable volume chamber adjacent said first vane, connection means connecting said gas intake conduit to a gas source to be evacuated, means for introducing liquid only into said second variable voltune chamber through said liquid intake conduit, first seal means including said rotor in coopera-tion with said housing, said liquid and the rotation of said rotor for continuously maintaining a liquid pressure and seal at said first interface to maintain a high differential pressure between said gas intake conduit and said liquid exhaust conduit, said continuous introduction of liquid through said liquid intake conduit into said second variable volume chamber adjacent said second vane comprising second seal means at said second interface to maintain a high differential pressure between said gas exhaust conduit and said liquid intake conduit.

8. A vacuum pump comprising a housing having a lobed rotor rotatably mounted therein, a wall within said housing defining a slot, a vane movable wit-hin said slot and engageable at its inner extremity with said rotor to form an interface therebetween, means urging said vane into engagement with said rotor, means for introducing and maintaining only a liquid on a first side of said interface and means for introducing and maintaining only a gas on a second side of said interface, said gas being at a lower pressure than said liquid, seal means at said interface to prevent passage of gas from said second side thereof to said first side and including only said liquid on said first side of said interface.

References Cited in the file of this patent UNITED STATES PATENTS 1,770,141 Meyer July 8, 1930 1,983,034 Hutchison Dec. 4, 1934 2,268,448 Groll Dec. 30, 1941 2,280,272 Sullivan Apr. 2l, 1942 2,342,088 sappi Feb. i5, i944 FOREIGN PATENTS 203,978 Great Britain Sept. 20, 1923 

